systemd.kill

package: systemd

title: systemd.kill(5)

summary: Process killing procedure configuration

text:
# systemd.kill(5)

## NAME
systemd.kill - Process killing procedure configuration

## SYNOPSIS
service.service, socket.socket, mount.mount, swap.swap, scope.scope

## DESCRIPTION
Unit configuration files for services, sockets, mount points, swap devices and scopes share a subset of configuration options which define the killing procedure of processes belonging to the unit.

This man page lists the configuration options shared by these five unit types. See systemd.unit(5) for the common options shared by all unit configuration files, and systemd.service(5), systemd.socket(5), systemd.swap(5), systemd.mount(5) and systemd.scope(5) for more information on the configuration file options specific to each unit type.

The kill procedure configuration options are configured in the [Service], [Socket], [Mount] or [Swap] section, depending on the unit type.

## OPTIONS
KillMode=

Specifies how processes of this unit shall be killed. One of control-group, mixed, process, none. If set to control-group, all remaining processes in the control group of this unit will be killed on unit stop (for services: after the stop command is executed, as configured with ExecStop=). If set to mixed, the SIGTERM signal (see below) is sent to the main process while the subsequent SIGKILL signal (see below) is sent to all remaining processes of the unit's control group. If set to process, only the main process itself is killed (not recommended!). If set to none, no process is killed (strongly recommended against!). In this case, only the stop command will be executed on unit stop, but no process will be killed otherwise. Processes remaining alive after stop are left in their control group and the control group continues to exist after stop unless empty.

Note that it is not recommended to set KillMode= to process or even none, as this allows processes to escape the service manager's lifecycle and resource management, and to remain running even while their service is considered stopped and is assumed to not consume any resources.

Processes will first be terminated via SIGTERM (unless the signal to send is changed via KillSignal= or RestartKillSignal=). Optionally, this is immediately followed by a SIGHUP (if enabled with SendSIGHUP=). If processes still remain after the main process of a unit has exited or the delay configured via the TimeoutStopSec= has passed, the termination request is repeated with the SIGKILL signal or the signal specified via FinalKillSignal= (unless this is disabled via the SendSIGKILL= option). See kill(2) for more information.

Defaults to control-group.

KillSignal=

Specifies which signal to use when stopping a service. This controls the signal that is sent as first step of shutting down a unit (see above), and is usually followed by SIGKILL (see above and below). For a list of valid signals, see signal(7). Defaults to SIGTERM. Note that, right after sending the signal specified in this setting, systemd will always send SIGCONT, to ensure that even suspended tasks can be terminated cleanly.

RestartKillSignal=

Specifies which signal to use when restarting a service. The same as KillSignal= described above, with the exception that this setting is used in a restart job. Not set by default, and the value of KillSignal= is used.

SendSIGHUP=

Specifies whether to send SIGHUP to remaining processes immediately after sending the signal configured with KillSignal=. This is useful to indicate to shells and shell-like programs that their connection has been severed. Takes a boolean value. Defaults to "no".

SendSIGKILL=

Specifies whether to send SIGKILL (or the signal specified by FinalKillSignal=) to remaining processes after a timeout, if the normal shutdown procedure left processes of the service around. When disabled, a KillMode= of control-group or mixed service will not restart if processes from prior services exist within the control group. Takes a boolean value. Defaults to "yes".

FinalKillSignal=

Specifies which signal to send to remaining processes after a timeout if SendSIGKILL= is enabled. The signal configured here should be one that is not typically caught and processed by services (SIGTERM is not suitable). Developers can find it useful to use this to generate a coredump to troubleshoot why a service did not terminate upon receiving the initial SIGTERM signal. This can be achieved by configuring LimitCORE= and setting FinalKillSignal= to either SIGQUIT or SIGABRT. Defaults to SIGKILL.

WatchdogSignal=

Specifies which signal to use to terminate the service when the watchdog timeout expires (enabled through WatchdogSec=). Defaults to SIGABRT.

## SEE ALSO
systemd(1), systemctl(1), journalctl(1), systemd.unit(5), systemd.service(5), systemd.socket(5), systemd.swap(5), systemd.mount(5), systemd.exec(5), systemd.directives(7), kill(2), signal(7)


systemd.mount

title: systemd.mount(5)

summary: Mount unit configuration

text:
# systemd.mount(5)

## NAME
systemd.mount - Mount unit configuration

## SYNOPSIS
mount.mount

## DESCRIPTION
A unit configuration file whose name ends in ".mount" encodes information about a file system mount point controlled and supervised by systemd.

This man page lists the configuration options specific to this unit type. See systemd.unit(5) for the common options of all unit configuration files. The common configuration items are configured in the generic [Unit] and [Install] sections. The mount specific configuration options are configured in the [Mount] section.

Additional options are listed in systemd.exec(5), which define the execution environment the mount(8) program is executed in, and in systemd.kill(5), which define the way the processes are terminated, and in systemd.resource-control(5), which configure resource control settings for the processes of the service.

Note that the options User= and Group= are not useful for mount units. systemd passes two parameters to mount(8); the values of What= and Where=. When invoked in this way, mount(8) does not read any options from /etc/fstab, and must be run as UID 0.

Mount units must be named after the mount point directories they control. Example: the mount point /home/lennart must be configured in a unit file home-lennart.mount. For details about the escaping logic used to convert a file system path to a unit name, see systemd.unit(5). Note that mount units cannot be templated, nor is possible to add multiple names to a mount unit by creating additional symlinks to it.

Optionally, a mount unit may be accompanied by an automount unit, to allow on-demand or parallelized mounting. See systemd.automount(5).

Mount points created at runtime (independently of unit files or /etc/fstab) will be monitored by systemd and appear like any other mount unit in systemd. See /proc/self/mountinfo description in proc(5).

Some file systems have special semantics as API file systems for kernel-to-userspace and userspace-to-userspace interfaces. Some of them may not be changed via mount units, and cannot be disabled. For a longer discussion see API File Systems[1].

The systemd-mount(1) command allows creating .mount and .automount units dynamically and transiently from the command line.

## AUTOMATIC DEPENDENCIES

### Implicit Dependencies
The following dependencies are implicitly added:

•If a mount unit is beneath another mount unit in the file system hierarchy, both a requirement dependency and an ordering dependency between both units are created automatically.

•Block device backed file systems automatically gain BindsTo= and After= type dependencies on the device unit encapsulating the block device (see below).

•If traditional file system quota is enabled for a mount unit, automatic Wants= and Before= dependencies on systemd-quotacheck.service and quotaon.service are added.

•Additional implicit dependencies may be added as result of execution and resource control parameters as documented in systemd.exec(5) and systemd.resource-control(5).

### Default Dependencies
The following dependencies are added unless DefaultDependencies=no is set:

•All mount units acquire automatic Before= and Conflicts= on umount.target in order to be stopped during shutdown.

•Mount units referring to local file systems automatically gain an After= dependency on local-fs-pre.target, and a Before= dependency on local-fs.target unless nofail mount option is set.

•Network mount units automatically acquire After= dependencies on remote-fs-pre.target, network.target and network-online.target, and gain a Before= dependency on remote-fs.target unless nofail mount option is set. Towards the latter a Wants= unit is added as well.

Mount units referring to local and network file systems are distinguished by their file system type specification. In some cases this is not sufficient (for example network block device based mounts, such as iSCSI), in which case _netdev may be added to the mount option string of the unit, which forces systemd to consider the mount unit a network mount.

## FSTAB
Mount units may either be configured via unit files, or via /etc/fstab (see fstab(5) for details). Mounts listed in /etc/fstab will be converted into native units dynamically at boot and when the configuration of the system manager is reloaded. In general, configuring mount points through /etc/fstab is the preferred approach. See systemd-fstab-generator(8) for details about the conversion.

The NFS mount option bg for NFS background mounts as documented in nfs(5) is detected by systemd-fstab-generator and the options are transformed so that systemd fulfills the job-control implications of that option. Specifically systemd-fstab-generator acts as though "x-systemd.mount-timeout=infinity,retry=10000" was prepended to the option list, and "fg,nofail" was appended. Depending on specific requirements, it may be appropriate to provide some of these options explicitly, or to make use of the "x-systemd.automount" option described below instead of using "bg".

When reading /etc/fstab a few special mount options are understood by systemd which influence how dependencies are created for mount points. systemd will create a dependency of type Wants= or Requires= (see option nofail below), from either local-fs.target or remote-fs.target, depending whether the file system is local or remote.

x-systemd.requires=

Configures a Requires= and an After= dependency between the created mount unit and another systemd unit, such as a device or mount unit. The argument should be a unit name, or an absolute path to a device node or mount point. This option may be specified more than once. This option is particularly useful for mount point declarations that need an additional device to be around (such as an external journal device for journal file systems) or an additional mount to be in place (such as an overlay file system that merges multiple mount points). See After= and Requires= in systemd.unit(5) for details. Note that this option always applies to the created mount unit only regardless whether x-systemd.automount has been specified.

x-systemd.before=, x-systemd.after=

In the created mount unit, configures a Before= or After= dependency on another systemd unit, such as a mount unit. The argument should be a unit name or an absolute path to a mount point. This option may be specified more than once. This option is particularly useful for mount point declarations with nofail option that are mounted asynchronously but need to be mounted before or after some unit start, for example, before local-fs.target unit. See Before= and After= in systemd.unit(5) for details. Note that these options always apply to the created mount unit only regardless whether x-systemd.automount has been specified.

x-systemd.wanted-by=, x-systemd.required-by=

In the created mount unit, configures a WantedBy= or RequiredBy= dependency on another unit. This option may be specified more than once. If this is specified, the normal automatic dependencies on the created mount unit, e.g., local-fs.target, are not automatically created. See WantedBy= and RequiredBy= in systemd.unit(5) for details.

x-systemd.requires-mounts-for=

Configures a RequiresMountsFor= dependency between the created mount unit and other mount units. The argument must be an absolute path. This option may be specified more than once. See RequiresMountsFor= in systemd.unit(5) for details.

x-systemd.device-bound

The block device backed file system will be upgraded to BindsTo= dependency. This option is only useful when mounting file systems manually with mount(8) as the default dependency in this case is Requires=. This option is already implied by entries in /etc/fstab or by mount units.

x-systemd.automount

An automount unit will be created for the file system. See systemd.automount(5) for details.

x-systemd.idle-timeout=

Configures the idle timeout of the automount unit. See TimeoutIdleSec= in systemd.automount(5) for details.

x-systemd.device-timeout=

Configure how long systemd should wait for a device to show up before giving up on an entry from /etc/fstab. Specify a time in seconds or explicitly append a unit such as "s", "min", "h", "ms". Note that this option can only be used in /etc/fstab, and will be ignored when part of the Options= setting in a unit file.

x-systemd.mount-timeout=

Configure how long systemd should wait for the mount command to finish before giving up on an entry from /etc/fstab. Specify a time in seconds or explicitly append a unit such as "s", "min", "h", "ms". Note that this option can only be used in /etc/fstab, and will be ignored when part of the Options= setting in a unit file.

See TimeoutSec= below for details.

x-systemd.makefs

The file system will be initialized on the device. If the device is not "empty", i.e. it contains any signature, the operation will be skipped. It is hence expected that this option remains set even after the device has been initialized. Note that this option can only be used in /etc/fstab, and will be ignored when part of the Options= setting in a unit file.

See systemd-makefs@.service(8).

wipefs(8) may be used to remove any signatures from a block device to force x-systemd.makefs to reinitialize the device.

x-systemd.growfs

The file system will be grown to occupy the full block device. If the file system is already at maximum size, no action will be performed. It is hence expected that this option remains set even after the file system has been grown. Only certain file system types are supported, see systemd-makefs@.service(8) for details. Note that this option can only be used in /etc/fstab, and will be ignored when part of the Options= setting in a unit file.

x-systemd.rw-only

If a mount operation fails to mount the file system read-write, it normally tries mounting the file system read-only instead. This option disables that behaviour, and causes the mount to fail immediately instead. This option is translated into the ReadWriteOnly= setting in a unit file.

_netdev

Normally the file system type is used to determine if a mount is a "network mount", i.e. if it should only be started after the network is available. Using this option overrides this detection and specifies that the mount requires network. Network mount units are ordered between remote-fs-pre.target and remote-fs.target, instead of local-fs-pre.target and local-fs.target. They also pull in network-online.target and are ordered after it and network.target.

noauto, auto

With noauto, the mount unit will not be added as a dependency for local-fs.target or remote-fs.target. This means that it will not be mounted automatically during boot, unless it is pulled in by some other unit. The auto option has the opposite meaning and is the default. Note that if x-systemd.automount (see above) is used, neither auto nor noauto have any effect. The matching automount unit will be added as a dependency to the appropriate target.

nofail

With nofail, this mount will be only wanted, not required, by local-fs.target or remote-fs.target. Moreover the mount unit is not ordered before these target units. This means that the boot will continue without waiting for the mount unit and regardless whether the mount point can be mounted successfully.

x-initrd.mount

An additional filesystem to be mounted in the initramfs. See initrd-fs.target description in systemd.special(7).

If a mount point is configured in both /etc/fstab and a unit file that is stored below /usr/, the former will take precedence. If the unit file is stored below /etc/, it will take precedence. This means: native unit files take precedence over traditional configuration files, but this is superseded by the rule that configuration in /etc/ will always take precedence over configuration in /usr/.

## OPTIONS
Mount files must include a [Mount] section, which carries information about the file system mount points it supervises. A number of options that may be used in this section are shared with other unit types. These options are documented in systemd.exec(5) and systemd.kill(5). The options specific to the [Mount] section of mount units are the following:

What=

Takes an absolute path of a device node, file or other resource to mount. See mount(8) for details. If this refers to a device node, a dependency on the respective device unit is automatically created. (See systemd.device(5) for more information.) This option is mandatory. Note that the usual specifier expansion is applied to this setting, literal percent characters should hence be written as "%%". If this mount is a bind mount and the specified path does not exist yet it is created as directory.

Where=

Takes an absolute path of a file or directory for the mount point; in particular, the destination cannot be a symbolic link. If the mount point does not exist at the time of mounting, it is created as either a directory or a file. The former is the usual case; the latter is done only if this mount is a bind mount and the source (What=) is not a directory. This string must be reflected in the unit filename. (See above.) This option is mandatory.

Type=

Takes a string for the file system type. See mount(8) for details. This setting is optional.

Options=

Mount options to use when mounting. This takes a comma-separated list of options. This setting is optional. Note that the usual specifier expansion is applied to this setting, literal percent characters should hence be written as "%%".

SloppyOptions=

Takes a boolean argument. If true, parsing of the options specified in Options= is relaxed, and unknown mount options are tolerated. This corresponds with mount(8)'s -s switch. Defaults to off.

LazyUnmount=

Takes a boolean argument. If true, detach the filesystem from the filesystem hierarchy at time of the unmount operation, and clean up all references to the filesystem as soon as they are not busy anymore. This corresponds with umount(8)'s -l switch. Defaults to off.

ReadWriteOnly=

Takes a boolean argument. If false, a mount point that shall be mounted read-write but cannot be mounted so is retried to be mounted read-only. If true the operation will fail immediately after the read-write mount attempt did not succeed. This corresponds with mount(8)'s -w switch. Defaults to off.

ForceUnmount=

Takes a boolean argument. If true, force an unmount (in case of an unreachable NFS system). This corresponds with umount(8)'s -f switch. Defaults to off.

DirectoryMode=

Directories of mount points (and any parent directories) are automatically created if needed. This option specifies the file system access mode used when creating these directories. Takes an access mode in octal notation. Defaults to 0755.

TimeoutSec=

Configures the time to wait for the mount command to finish. If a command does not exit within the configured time, the mount will be considered failed and be shut down again. All commands still running will be terminated forcibly via SIGTERM, and after another delay of this time with SIGKILL. (See KillMode= in systemd.kill(5).) Takes a unit-less value in seconds, or a time span value such as "5min 20s". Pass 0 to disable the timeout logic. The default value is set from DefaultTimeoutStartSec= option in systemd-system.conf(5).

Check systemd.exec(5) and systemd.kill(5) for more settings.

## SEE ALSO
systemd(1), systemctl(1), systemd-system.conf(5), systemd.unit(5), systemd.exec(5), systemd.kill(5), systemd.resource-control(5), systemd.service(5), systemd.device(5), proc(5), mount(8), systemd-fstab-generator(8), systemd.directives(7), systemd-mount(1)

## NOTES
1.

API File Systems

https://www.freedesktop.org/wiki/Software/systemd/APIFileSystems


systemd.path

title: systemd.path(5)

summary: Path unit configuration

text:
# systemd.path(5)

## NAME
systemd.path - Path unit configuration

## SYNOPSIS
path.path

## DESCRIPTION
A unit configuration file whose name ends in ".path" encodes information about a path monitored by systemd, for path-based activation.

This man page lists the configuration options specific to this unit type. See systemd.unit(5) for the common options of all unit configuration files. The common configuration items are configured in the generic [Unit] and [Install] sections. The path specific configuration options are configured in the [Path] section.

For each path file, a matching unit file must exist, describing the unit to activate when the path changes. By default, a service by the same name as the path (except for the suffix) is activated. Example: a path file foo.path activates a matching service foo.service. The unit to activate may be controlled by Unit= (see below).

Internally, path units use the inotify(7) API to monitor file systems. Due to that, it suffers by the same limitations as inotify, and for example cannot be used to monitor files or directories changed by other machines on remote NFS file systems.

When a service unit triggered by a path unit terminates (regardless whether it exited successfully or failed), monitored paths are checked immediately again, and the service accordingly restarted instantly. As protection against busy looping in this trigger/start cycle, a start rate limit is enforced on the service unit, see StartLimitIntervalSec= and StartLimitBurst= in systemd.unit(5). Unlike other service failures, the error condition that the start rate limit is hit is propagated from the service unit to the path unit and causes the path unit to fail as well, thus ending the loop.

## AUTOMATIC DEPENDENCIES

### Implicit Dependencies
The following dependencies are implicitly added:

•If a path unit is beneath another mount unit in the file system hierarchy, both a requirement and an ordering dependency between both units are created automatically.

•An implicit Before= dependency is added between a path unit and the unit it is supposed to activate.

### Default Dependencies
The following dependencies are added unless DefaultDependencies=no is set:

•Path units will automatically have dependencies of type Before= on paths.target, dependencies of type After= and Requires= on sysinit.target, and have dependencies of type Conflicts= and Before= on shutdown.target. These ensure that path units are terminated cleanly prior to system shutdown. Only path units involved with early boot or late system shutdown should disable DefaultDependencies= option.

## OPTIONS
Path files must include a [Path] section, which carries information about the path(s) it monitors. The options specific to the [Path] section of path units are the following:

PathExists=, PathExistsGlob=, PathChanged=, PathModified=, DirectoryNotEmpty=

Defines paths to monitor for certain changes: PathExists= may be used to watch the mere existence of a file or directory. If the file specified exists, the configured unit is activated. PathExistsGlob= works similar, but checks for the existence of at least one file matching the globbing pattern specified. PathChanged= may be used to watch a file or directory and activate the configured unit whenever it changes. It is not activated on every write to the watched file but it is activated if the file which was open for writing gets closed. PathModified= is similar, but additionally it is activated also on simple writes to the watched file. DirectoryNotEmpty= may be used to watch a directory and activate the configured unit whenever it contains at least one file. The arguments of these directives must be absolute file system paths.

Multiple directives may be combined, of the same and of different types, to watch multiple paths. If the empty string is assigned to any of these options, the list of paths to watch is reset, and any prior assignments of these options will not have any effect.

If a path already exists (in case of PathExists= and PathExistsGlob=) or a directory already is not empty (in case of DirectoryNotEmpty=) at the time the path unit is activated, then the configured unit is immediately activated as well. Something similar does not apply to PathChanged= and PathModified=.

If the path itself or any of the containing directories are not accessible, systemd will watch for permission changes and notice that conditions are satisfied when permissions allow that.

Unit=

The unit to activate when any of the configured paths changes. The argument is a unit name, whose suffix is not ".path". If not specified, this value defaults to a service that has the same name as the path unit, except for the suffix. (See above.) It is recommended that the unit name that is activated and the unit name of the path unit are named identical, except for the suffix.

MakeDirectory=

Takes a boolean argument. If true, the directories to watch are created before watching. This option is ignored for PathExists= settings. Defaults to false.

DirectoryMode=

If MakeDirectory= is enabled, use the mode specified here to create the directories in question. Takes an access mode in octal notation. Defaults to 0755.

## SEE ALSO
systemd(1), systemctl(1), systemd.unit(5), systemd.service(5), inotify(7), systemd.directives(7)


systemd.preset

title: systemd.preset(5)

summary: Service enablement presets

text:
# systemd.preset(5)

## NAME
systemd.preset - Service enablement presets

## SYNOPSIS
/etc/systemd/system-preset/*.preset

/run/systemd/system-preset/*.preset

/lib/systemd/system-preset/*.preset

/etc/systemd/user-preset/*.preset

/run/systemd/user-preset/*.preset

/usr/lib/systemd/user-preset/*.preset

## DESCRIPTION
Preset files may be used to encode policy which units shall be enabled by default and which ones shall be disabled. They are read by systemctl preset which uses this information to enable or disable a unit. Depending on that policy, systemctl preset is identical to systemctl enable or systemctl disable. systemctl preset is used by the post install scriptlets of rpm packages (or other OS package formats), to enable/disable specific units by default on package installation, enforcing distribution, spin or administrator preset policy. This allows choosing a certain set of units to be enabled/disabled even before installing the actual package. For more information, see systemctl(1).

It is not recommended to ship preset files within the respective software packages implementing the units, but rather centralize them in a distribution or spin default policy, which can be amended by administrator policy, see below.

If no preset files exist, systemctl preset will enable all units that are installed by default. If this is not desired and all units shall rather be disabled, it is necessary to ship a preset file with a single, catchall "disable *" line. (See example 1, below.)

## PRESET FILE FORMAT
The preset files contain a list of directives consisting of either the word "enable" or "disable" followed by a space and a unit name (possibly with shell style wildcards), separated by newlines. Empty lines and lines whose first non-whitespace character is "#" or ";" are ignored. Multiple instance names for unit templates may be specified as a space separated list at the end of the line instead of the customary position between "@" and the unit suffix.

Presets must refer to the "real" unit file, and not to any aliases. See systemd.unit(5) for a description of unit aliasing.

Two different directives are understood: "enable" may be used to enable units by default, "disable" to disable units by default.

If multiple lines apply to a unit name, the first matching one takes precedence over all others.

Each preset file shall be named in the style of <priority>-<policy-name>.preset. Files in /etc/ override files with the same name in /lib/ and /run/. Files in /run/ override files with the same name in /lib/. Packages should install their preset files in /lib/. Files in /etc/ are reserved for the local administrator, who may use this logic to override the preset files installed by vendor packages. All preset files are sorted by their filename in lexicographic order, regardless of which of the directories they reside in. If multiple files specify the same unit name, the entry in the file with the lexicographically earliest name will be applied. It is recommended to prefix all filenames with a two-digit number and a dash, to simplify the ordering of the files.

If the administrator wants to disable a preset file supplied by the vendor, the recommended way is to place a symlink to /dev/null in /etc/systemd/system-preset/ bearing the same filename.

## EXAMPLES
Example 1. Default to off

```
# /lib/systemd/system-preset/99-default.preset
disable *
```

This disables all units. Due to the filename prefix "99-", it will be read last and hence can easily be overridden by spin or administrator preset policy.

Example 2. Enable multiple template instances

```
# /lib/systemd/system-preset/80-dirsrv.preset
enable dirsrv@.service foo bar baz
```

This enables all three of dirsrv@foo.service, dirsrv@bar.service and dirsrv@baz.service.

Example 3. A GNOME spin

```
# /lib/systemd/system-preset/50-gnome.preset
enable gdm.service
enable colord.service
enable accounts-daemon.service
enable avahi-daemon.*
```

This enables the three mentioned units, plus all avahi-daemon regardless of which unit type. A file like this could be useful for inclusion in a GNOME spin of a distribution. It will ensure that the units necessary for GNOME are properly enabled as they are installed. It leaves all other units untouched, and subject to other (later) preset files, for example like the one from the first example above.

Example 4. Administrator policy

```
# /etc/systemd/system-preset/00-lennart.preset
enable httpd.service
enable sshd.service
enable postfix.service
disable *
```

This enables three specific services and disables all others. This is useful for administrators to specifically select the units to enable, and disable all others. Due to the filename prefix "00-" it will be read early and override all other preset policy files.

## MOTIVATION FOR THE PRESET LOGIC
Different distributions have different policies on which services shall be enabled by default when the package they are shipped in is installed. On Fedora all services stay off by default, so that installing a package will not cause a service to be enabled (with some exceptions). On Debian all services are immediately enabled by default, so that installing a package will cause its services to be enabled right-away.

Even within a single distribution, different spins (flavours, remixes, whatever you might want to call them) of a distribution also have different policies on what services to enable, and what services to leave off. For example, Fedora Workstation will enable gdm as display manager by default, while the Fedora KDE spin will enable sddm instead.

Different sites might also have different policies what to turn on by default and what to turn off. For example, one administrator would prefer to enforce the policy of "sshd should be always on, but everything else off", while another one might say "snmpd always on, and for everything else use the distribution policy defaults".

Traditionally, policy about which services shall be enabled were implemented in each package individually. This made it cumbersome to implement different policies per spin or per site, or to create software packages that do the right thing on more than one distribution. The enablement mechanism was also encoding the enablement policy.

The preset mechanism allows clean separation of the enablement mechanism (inside the package scriptlets, by invoking systemctl preset) and enablement policy (centralized in the preset files), and lifts the configuration out of individual packages. Preset files may be written for specific distributions, for specific spins or for specific sites, in order to enforce different policies as needed. It is recommended to apply the policy encoded in preset files in package installation scriptlets.

## SEE ALSO
systemd(1), systemctl(1), systemd-delta(1)

daemon(7) has a discussion of packaging scriptlets.

Fedora page introducing the use of presets: Features/PackagePresets[1].

## NOTES
1.

Features/PackagePresets

https://fedoraproject.org/wiki/Features/PackagePresets


systemd.resource-control

title: systemd.resource-control(5)

summary: Resource control unit settings

text:
# systemd.resource-control(5)

## NAME
systemd.resource-control - Resource control unit settings

## SYNOPSIS
slice.slice, scope.scope, service.service, socket.socket, mount.mount, swap.swap

## DESCRIPTION
Unit configuration files for services, slices, scopes, sockets, mount points, and swap devices share a subset of configuration options for resource control of spawned processes. Internally, this relies on the Linux Control Groups (cgroups) kernel concept for organizing processes in a hierarchical tree of named groups for the purpose of resource management.

This man page lists the configuration options shared by those six unit types. See systemd.unit(5) for the common options of all unit configuration files, and systemd.slice(5), systemd.scope(5), systemd.service(5), systemd.socket(5), systemd.mount(5), and systemd.swap(5) for more information on the specific unit configuration files. The resource control configuration options are configured in the [Slice], [Scope], [Service], [Socket], [Mount], or [Swap] sections, depending on the unit type.

In addition, options which control resources available to programs executed by systemd are listed in systemd.exec(5). Those options complement options listed here.

See the New Control Group Interfaces[1] for an introduction on how to make use of resource control APIs from programs.

### Setting resource controls for a group of related units
As described in systemd.unit(5), the settings listed here may be set through the main file of a unit and drop-in snippets in *.d/ directories. The list of directories searched for drop-ins includes names formed by repeatedly truncating the unit name after all dashes. This is particularly convenient to set resource limits for a group of units with similar names.

For example, every user gets their own slice user-nnn.slice. Drop-ins with local configuration that affect user 1000 may be placed in /etc/systemd/system/user-1000.slice, /etc/systemd/system/user-1000.slice.d/*.conf, but also /etc/systemd/system/user-.slice.d/*.conf. This last directory applies to all user slices.

## IMPLICIT DEPENDENCIES
The following dependencies are implicitly added:

•Units with the Slice= setting set automatically acquire Requires= and After= dependencies on the specified slice unit.

## UNIFIED AND LEGACY CONTROL GROUP HIERARCHIES
The unified control group hierarchy is the new version of kernel control group interface, see Control Groups v2[2]. Depending on the resource type, there are differences in resource control capabilities. Also, because of interface changes, some resource types have separate set of options on the unified hierarchy.

CPU

CPUWeight= and StartupCPUWeight= replace CPUShares= and StartupCPUShares=, respectively. The "cpuacct" controller does not exist separately on the unified hierarchy.

Memory

MemoryMax= replaces MemoryLimit=. MemoryLow= and MemoryHigh= are effective only on unified hierarchy.

IO

"IO"-prefixed settings are a superset of and replace "BlockIO"-prefixed ones. On unified hierarchy, IO resource control also applies to buffered writes.

To ease the transition, there is best-effort translation between the two versions of settings. For each controller, if any of the settings for the unified hierarchy are present, all settings for the legacy hierarchy are ignored. If the resulting settings are for the other type of hierarchy, the configurations are translated before application.

Legacy control group hierarchy (see Control Groups version 1[3]), also called cgroup-v1, doesn't allow safe delegation of controllers to unprivileged processes. If the system uses the legacy control group hierarchy, resource control is disabled for the systemd user instance, see systemd(1).

## OPTIONS
Units of the types listed above can have settings for resource control configuration:

CPUAccounting=

Turn on CPU usage accounting for this unit. Takes a boolean argument. Note that turning on CPU accounting for one unit will also implicitly turn it on for all units contained in the same slice and for all its parent slices and the units contained therein. The system default for this setting may be controlled with DefaultCPUAccounting= in systemd-system.conf(5).

CPUWeight=weight, StartupCPUWeight=weight

Assign the specified CPU time weight to the processes executed, if the unified control group hierarchy is used on the system. These options take an integer value and control the "cpu.weight" control group attribute. The allowed range is 1 to 10000. Defaults to 100. For details about this control group attribute, see Control Groups v2[2] and CFS Scheduler[4]. The available CPU time is split up among all units within one slice relative to their CPU time weight. A higher weight means more CPU time, a lower weight means less. While StartupCPUWeight= only applies to the startup phase of the system, CPUWeight= applies to normal runtime of the system, and if the former is not set also to the startup phase. Using StartupCPUWeight= allows prioritizing specific services at boot-up differently than during normal runtime.

These settings replace CPUShares= and StartupCPUShares=.

CPUQuota=

Assign the specified CPU time quota to the processes executed. Takes a percentage value, suffixed with "%". The percentage specifies how much CPU time the unit shall get at maximum, relative to the total CPU time available on one CPU. Use values > 100% for allotting CPU time on more than one CPU. This controls the "cpu.max" attribute on the unified control group hierarchy and "cpu.cfs_quota_us" on legacy. For details about these control group attributes, see Control Groups v2[2] and sched-bwc.txt[5]. Setting CPUQuota= to an empty value unsets the quota. Example: CPUQuota=20% ensures that the executed processes will never get more than 20% CPU time on one CPU.

CPUQuotaPeriodSec=

Assign the duration over which the CPU time quota specified by CPUQuota= is measured. Takes a time duration value in seconds, with an optional suffix such as "ms" for milliseconds (or "s" for seconds.) The default setting is 100ms. The period is clamped to the range supported by the kernel, which is [1ms, 1000ms]. Additionally, the period is adjusted up so that the quota interval is also at least 1ms. Setting CPUQuotaPeriodSec= to an empty value resets it to the default. This controls the second field of "cpu.max" attribute on the unified control group hierarchy and "cpu.cfs_period_us" on legacy. For details about these control group attributes, see Control Groups v2[2] and CFS Scheduler[4].

Example: CPUQuotaPeriodSec=10ms to request that the CPU quota is measured in periods of 10ms.

AllowedCPUs=

Restrict processes to be executed on specific CPUs. Takes a list of CPU indices or ranges separated by either whitespace or commas. CPU ranges are specified by the lower and upper CPU indices separated by a dash. Setting AllowedCPUs= doesn't guarantee that all of the CPUs will be used by the processes as it may be limited by parent units. The effective configuration is reported as EffectiveCPUs=.

This setting is supported only with the unified control group hierarchy.

AllowedMemoryNodes=

Restrict processes to be executed on specific memory NUMA nodes. Takes a list of memory NUMA nodes indices or ranges separated by either whitespace or commas. Memory NUMA nodes ranges are specified by the lower and upper NUMA nodes indices separated by a dash. Setting AllowedMemoryNodes= doesn't guarantee that all of the memory NUMA nodes will be used by the processes as it may be limited by parent units. The effective configuration is reported as EffectiveMemoryNodes=.

This setting is supported only with the unified control group hierarchy.

MemoryAccounting=

Turn on process and kernel memory accounting for this unit. Takes a boolean argument. Note that turning on memory accounting for one unit will also implicitly turn it on for all units contained in the same slice and for all its parent slices and the units contained therein. The system default for this setting may be controlled with DefaultMemoryAccounting= in systemd-system.conf(5).

MemoryMin=bytes, MemoryLow=bytes

Specify the memory usage protection of the executed processes in this unit. When reclaiming memory, the unit is treated as if it was using less memory resulting in memory to be preferentially reclaimed from unprotected units. Using MemoryLow= results in a weaker protection where memory may still be reclaimed to avoid invoking the OOM killer in case there is no other reclaimable memory. For a protection to be effective, it is generally required to set a corresponding allocation on all ancestors, which is then distributed between children (with the exception of the root slice). Any MemoryMin= or MemoryLow= allocation that is not explicitly distributed to specific children is used to create a shared protection for all children. As this is a shared protection, the children will freely compete for the memory.

Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size is parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. Alternatively, a percentage value may be specified, which is taken relative to the installed physical memory on the system. If assigned the special value "infinity", all available memory is protected, which may be useful in order to always inherit all of the protection afforded by ancestors. This controls the "memory.min" or "memory.low" control group attribute. For details about this control group attribute, see Memory Interface Files[6].

This setting is supported only if the unified control group hierarchy is used and disables MemoryLimit=.

Units may have their children use a default "memory.min" or "memory.low" value by specifying DefaultMemoryMin= or DefaultMemoryLow=, which has the same semantics as MemoryMin= and MemoryLow=. This setting does not affect "memory.min" or "memory.low" in the unit itself. Using it to set a default child allocation is only useful on kernels older than 5.7, which do not support the "memory_recursiveprot" cgroup2 mount option.

MemoryHigh=bytes

Specify the throttling limit on memory usage of the executed processes in this unit. Memory usage may go above the limit if unavoidable, but the processes are heavily slowed down and memory is taken away aggressively in such cases. This is the main mechanism to control memory usage of a unit. Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size is parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. Alternatively, a percentage value may be specified, which is taken relative to the installed physical memory on the system. If assigned the special value "infinity", no memory throttling is applied. This controls the "memory.high" control group attribute. For details about this control group attribute, see Memory Interface Files[6].

This setting is supported only if the unified control group hierarchy is used and disables MemoryLimit=.

MemoryMax=bytes

Specify the absolute limit on memory usage of the executed processes in this unit. If memory usage cannot be contained under the limit, out-of-memory killer is invoked inside the unit. It is recommended to use MemoryHigh= as the main control mechanism and use MemoryMax= as the last line of defense. Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size is parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. Alternatively, a percentage value may be specified, which is taken relative to the installed physical memory on the system. If assigned the special value "infinity", no memory limit is applied. This controls the "memory.max" control group attribute. For details about this control group attribute, see Memory Interface Files[6].

This setting replaces MemoryLimit=.

MemorySwapMax=bytes

Specify the absolute limit on swap usage of the executed processes in this unit. Takes a swap size in bytes. If the value is suffixed with K, M, G or T, the specified swap size is parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. If assigned the special value "infinity", no swap limit is applied. This controls the "memory.swap.max" control group attribute. For details about this control group attribute, see Memory Interface Files[6].

This setting is supported only if the unified control group hierarchy is used and disables MemoryLimit=.

TasksAccounting=

Turn on task accounting for this unit. Takes a boolean argument. If enabled, the system manager will keep track of the number of tasks in the unit. The number of tasks accounted this way includes both kernel threads and userspace processes, with each thread counting individually. Note that turning on tasks accounting for one unit will also implicitly turn it on for all units contained in the same slice and for all its parent slices and the units contained therein. The system default for this setting may be controlled with DefaultTasksAccounting= in systemd-system.conf(5).

TasksMax=N

Specify the maximum number of tasks that may be created in the unit. This ensures that the number of tasks accounted for the unit (see above) stays below a specific limit. This either takes an absolute number of tasks or a percentage value that is taken relative to the configured maximum number of tasks on the system. If assigned the special value "infinity", no tasks limit is applied. This controls the "pids.max" control group attribute. For details about this control group attribute, see Process Number Controller[7]. The system default for this setting may be controlled with DefaultTasksMax= in systemd-system.conf(5).

IOAccounting=

Turn on Block I/O accounting for this unit, if the unified control group hierarchy is used on the system. Takes a boolean argument. Note that turning on block I/O accounting for one unit will also implicitly turn it on for all units contained in the same slice and all for its parent slices and the units contained therein. The system default for this setting may be controlled with DefaultIOAccounting= in systemd-system.conf(5). This setting replaces BlockIOAccounting= and disables settings prefixed with BlockIO or StartupBlockIO.

IOWeight=weight, StartupIOWeight=weight

Set the default overall block I/O weight for the executed processes, if the unified control group hierarchy is used on the system. Takes a single weight value (between 1 and 10000) to set the default block I/O weight. This controls the "io.weight" control group attribute, which defaults to 100. For details about this control group attribute, see IO Interface Files[8]. The available I/O bandwidth is split up among all units within one slice relative to their block I/O weight. A higher weight means more I/O bandwidth, a lower weight means less. While StartupIOWeight= only applies to the startup phase of the system, IOWeight= applies to the later runtime of the system, and if the former is not set also to the startup phase. This allows prioritizing specific services at boot-up differently than during runtime.

These settings replace BlockIOWeight= and StartupBlockIOWeight= and disable settings prefixed with BlockIO or StartupBlockIO.

IODeviceWeight=device weight

Set the per-device overall block I/O weight for the executed processes, if the unified control group hierarchy is used on the system. Takes a space-separated pair of a file path and a weight value to specify the device specific weight value, between 1 and 10000. (Example: "/dev/sda 1000"). The file path may be specified as path to a block device node or as any other file, in which case the backing block device of the file system of the file is determined. This controls the "io.weight" control group attribute, which defaults to 100. Use this option multiple times to set weights for multiple devices. For details about this control group attribute, see IO Interface Files[8]. This setting replaces BlockIODeviceWeight= and disables settings prefixed with BlockIO or StartupBlockIO.

The specified device node should reference a block device that has an I/O scheduler associated, i.e. should not refer to partition or loopback block devices, but to the originating, physical device. When a path to a regular file or directory is specified it is attempted to discover the correct originating device backing the file system of the specified path. This works correctly only for simpler cases, where the file system is directly placed on a partition or physical block device, or where simple 1:1 encryption using dm-crypt/LUKS is used. This discovery does not cover complex storage and in particular RAID and volume management storage devices.

IOReadBandwidthMax=device bytes, IOWriteBandwidthMax=device bytes

Set the per-device overall block I/O bandwidth maximum limit for the executed processes, if the unified control group hierarchy is used on the system. This limit is not work-conserving and the executed processes are not allowed to use more even if the device has idle capacity. Takes a space-separated pair of a file path and a bandwidth value (in bytes per second) to specify the device specific bandwidth. The file path may be a path to a block device node, or as any other file in which case the backing block device of the file system of the file is used. If the bandwidth is suffixed with K, M, G, or T, the specified bandwidth is parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes, respectively, to the base of 1000. (Example: "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 5M"). This controls the "io.max" control group attributes. Use this option multiple times to set bandwidth limits for multiple devices. For details about this control group attribute, see IO Interface Files[8]. These settings replace BlockIOReadBandwidth= and BlockIOWriteBandwidth= and disable settings prefixed with BlockIO or StartupBlockIO.

Similar restrictions on block device discovery as for IODeviceWeight= apply, see above.

IOReadIOPSMax=device IOPS, IOWriteIOPSMax=device IOPS

Set the per-device overall block I/O IOs-Per-Second maximum limit for the executed processes, if the unified control group hierarchy is used on the system. This limit is not work-conserving and the executed processes are not allowed to use more even if the device has idle capacity. Takes a space-separated pair of a file path and an IOPS value to specify the device specific IOPS. The file path may be a path to a block device node, or as any other file in which case the backing block device of the file system of the file is used. If the IOPS is suffixed with K, M, G, or T, the specified IOPS is parsed as KiloIOPS, MegaIOPS, GigaIOPS, or TeraIOPS, respectively, to the base of 1000. (Example: "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 1K"). This controls the "io.max" control group attributes. Use this option multiple times to set IOPS limits for multiple devices. For details about this control group attribute, see IO Interface Files[8]. These settings are supported only if the unified control group hierarchy is used and disable settings prefixed with BlockIO or StartupBlockIO.

Similar restrictions on block device discovery as for IODeviceWeight= apply, see above.

IODeviceLatencyTargetSec=device target

Set the per-device average target I/O latency for the executed processes, if the unified control group hierarchy is used on the system. Takes a file path and a timespan separated by a space to specify the device specific latency target. (Example: "/dev/sda 25ms"). The file path may be specified as path to a block device node or as any other file, in which case the backing block device of the file system of the file is determined. This controls the "io.latency" control group attribute. Use this option multiple times to set latency target for multiple devices. For details about this control group attribute, see IO Interface Files[8]. Implies "IOAccounting=yes".

These settings are supported only if the unified control group hierarchy is used.

Similar restrictions on block device discovery as for IODeviceWeight= apply, see above.

IPAccounting=

Takes a boolean argument. If true, turns on IPv4 and IPv6 network traffic accounting for packets sent or received by the unit. When this option is turned on, all IPv4 and IPv6 sockets created by any process of the unit are accounted for. When this option is used in socket units, it applies to all IPv4 and IPv6 sockets associated with it (including both listening and connection sockets where this applies). Note that for socket-activated services, this configuration setting and the accounting data of the service unit and the socket unit are kept separate, and displayed separately. No propagation of the setting and the collected statistics is done, in either direction. Moreover, any traffic sent or received on any of the socket unit's sockets is accounted to the socket unit — and never to the service unit it might have activated, even if the socket is used by it.

The system default for this setting may be controlled with DefaultIPAccounting= in systemd-system.conf(5).

IPAddressAllow=ADDRESS[/PREFIXLENGTH]..., IPAddressDeny=ADDRESS[/PREFIXLENGTH]...

Turn on network traffic filtering for IP packets sent and received over AF_INET and AF_INET6 sockets. Both directives take a space separated list of IPv4 or IPv6 addresses, each optionally suffixed with an address prefix length in bits after a "/" character. If the suffix is omitted, the address is considered a host address, i.e. the filter covers the whole address (32 bits for IPv4, 128 bits for IPv6). The access lists configured with this option are applied to all sockets created by processes of this unit (or in the case of socket units, associated with it). The lists are implicitly combined with any lists configured for any of the parent slice units this unit might be a member of. By default both access lists are empty. Both ingress and egress traffic is filtered by these settings. In case of ingress traffic the source IP address is checked against these access lists, in case of egress traffic the destination IP address is checked. The following rules are applied in turn:

•Access is granted when the checked IP address matches an entry in the IPAddressAllow= list.

•Otherwise, access is denied when the checked IP address matches an entry in the IPAddressDeny= list.

•Otherwise, access is granted.

In order to implement an allow-listing IP firewall, it is recommended to use a IPAddressDeny=any setting on an upper-level slice unit (such as the root slice -.slice or the slice containing all system services system.slice – see systemd.special(7) for details on these slice units), plus individual per-service IPAddressAllow= lines permitting network access to relevant services, and only them.

Note that for socket-activated services, the IP access list configured on the socket unit applies to all sockets associated with it directly, but not to any sockets created by the ultimately activated services for it. Conversely, the IP access list configured for the service is not applied to any sockets passed into the service via socket activation. Thus, it is usually a good idea to replicate the IP access lists on both the socket and the service unit. Nevertheless, it may make sense to maintain one list more open and the other one more restricted, depending on the usecase.

If these settings are used multiple times in the same unit the specified lists are combined. If an empty string is assigned to these settings the specific access list is reset and all previous settings undone.

In place of explicit IPv4 or IPv6 address and prefix length specifications a small set of symbolic names may be used. The following names are defined:

Table 1. Special address/network names

Symbolic Name

Definition

Meaning

any

0.0.0.0/0 ::/0

Any host

localhost

127.0.0.0/8 ::1/128

All addresses on the local loopback

link-local

169.254.0.0/16 fe80::/64

All link-local IP addresses

multicast

224.0.0.0/4 ff00::/8

All IP multicasting addresses

Note that these settings might not be supported on some systems (for example if eBPF control group support is not enabled in the underlying kernel or container manager). These settings will have no effect in that case. If compatibility with such systems is desired it is hence recommended to not exclusively rely on them for IP security.

IPIngressFilterPath=BPF_FS_PROGRAM_PATH, IPEgressFilterPath=BPF_FS_PROGRAM_PATH

Add custom network traffic filters implemented as BPF programs, applying to all IP packets sent and received over AF_INET and AF_INET6 sockets. Takes an absolute path to a pinned BPF program in the BPF virtual filesystem (/sys/fs/bpf/). The filters configured with this option are applied to all sockets created by processes of this unit (or in the case of socket units, associated with it). The filters are loaded in addition to filters any of the parent slice units this unit might be a member of as well as any IPAddressAllow= and IPAddressDeny= filters in any of these units. By default there are no filters specified.

If these settings are used multiple times in the same unit all the specified programs are attached. If an empty string is assigned to these settings the program list is reset and all previous specified programs ignored.

If the path BPF_FS_PROGRAM_PATH in IPIngressFilterPath= assignment is already being handled by BPFProgram= ingress hook, e.g. BPFProgram=ingress:BPF_FS_PROGRAM_PATH, the assignment will be still considered valid and the program will be attached to a cgroup. Same for IPEgressFilterPath= path and egress hook.

Note that for socket-activated services, the IP filter programs configured on the socket unit apply to all sockets associated with it directly, but not to any sockets created by the ultimately activated services for it. Conversely, the IP filter programs configured for the service are not applied to any sockets passed into the service via socket activation. Thus, it is usually a good idea, to replicate the IP filter programs on both the socket and the service unit, however it often makes sense to maintain one configuration more open and the other one more restricted, depending on the usecase.

Note that these settings might not be supported on some systems (for example if eBPF control group support is not enabled in the underlying kernel or container manager). These settings will fail the service in that case. If compatibility with such systems is desired it is hence recommended to attach your filter manually (requires Delegate=yes) instead of using this setting.

BPFProgram=type:program-path

Add a custom cgroup BPF program. BPFProgram= allows attaching BPF hooks to the cgroup of a systemd unit. (This generalizes the functionality exposed via IPEgressFilterPath= for egress and IPIngressFilterPath= for ingress.) Cgroup-bpf hooks in the form of BPF programs loaded to the BPF filesystem are attached with cgroup-bpf attach flags determined by the unit. For details about attachment types and flags see https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/include/uapi/linux/bpf.h. For general BPF documentation please refer to https://www.kernel.org/doc/html/latest/bpf/index.html.

The specification of BPF program consists of a type followed by a program-path with ":" as the separator: type:program-path.

type is the string name of BPF attach type also used in bpftool. type can be one of egress, ingress, sock_create, sock_ops, device, bind4, bind6, connect4, connect6, post_bind4, post_bind6, sendmsg4, sendmsg6, sysctl, recvmsg4, recvmsg6, getsockopt, setsockopt.

Setting BPFProgram= to an empty value makes previous assignments ineffective.

Multiple assignments of the same type:program-path value have the same effect as a single assignment: the program with the path program-path will be attached to cgroup hook type just once.

If BPF egress pinned to program-path path is already being handled by IPEgressFilterPath=, BPFProgram= assignment will be considered valid and BPFProgram= will be attached to a cgroup. Similarly for ingress hook and IPIngressFilterPath= assignment.

BPF programs passed with BPFProgram= are attached to the cgroup of a unit with BPF attach flag multi, that allows further attachments of the same type within cgroup hierarchy topped by the unit cgroup.

Examples:

```
BPFProgram=egress:/sys/fs/bpf/egress-hook
BPFProgram=bind6:/sys/fs/bpf/sock-addr-hook
```

SocketBindAllow=bind-rule, SocketBindDeny=bind-rule

Allow or deny binding a socket address to a socket by matching it with the bind-rule and applying a corresponding action if there is a match. bind-rule describes socket properties such as address-family, transport-protocol and ip-ports.

bind-rule := { [address-family:][transport-protocol:][ip-ports] | any }

address-family := { ipv4 | ipv6 }

transport-protocol := { tcp | udp }

ip-ports := { ip-port | ip-port-range }

An optional address-family expects ipv4 or ipv6 values. If not specified, a rule will be matched for both IPv4 and IPv6 addresses and applied depending on other socket fields, e.g. transport-protocol, ip-port.

An optional transport-protocol expects tcp or udp transport protocol names. If not specified, a rule will be matched for any transport protocol.

An optional ip-port value must lie within 1...65535 interval inclusively, i.e. dynamic port 0 is not allowed. A range of sequential ports is described by ip-port-range := ip-port-low-ip-port-high, where ip-port-low is smaller than or equal to ip-port-high and both are within 1...65535 inclusively.

A special value any can be used to apply a rule to any address family, transport protocol and any port with a positive value.

To allow multiple rules assign SocketBindAllow= or SocketBindDeny= multiple times. To clear the existing assignments pass an empty SocketBindAllow= or SocketBindDeny= assignment.

For each of SocketBindAllow= and SocketBindDeny=, maximum allowed number of assignments is 128.

•Binding to a socket is allowed when a socket address matches an entry in the SocketBindAllow= list.

•Otherwise, binding is denied when the socket address matches an entry in the SocketBindDeny= list.

•Otherwise, binding is allowed.

The feature is implemented with cgroup/bind4 and cgroup/bind6 cgroup-bpf hooks.

Examples:

```
...
# Allow binding IPv6 socket addresses with a port greater than or equal to 10000.
[Service]
SocketBindAllow=ipv6:10000-65535
SocketBindDeny=any
...
# Allow binding IPv4 and IPv6 socket addresses with 1234 and 4321 ports.
[Service]
SocketBindAllow=1234
SocketBindAllow=4321
SocketBindDeny=any
...
# Deny binding IPv6 socket addresses.
[Service]
SocketBindDeny=ipv6
...
# Deny binding IPv4 and IPv6 socket addresses.
[Service]
SocketBindDeny=any
...
# Allow binding only over TCP
[Service]
SocketBindAllow=tcp
SocketBindDeny=any
...
# Allow binding only over IPv6/TCP
[Service]
SocketBindAllow=ipv6:tcp
SocketBindDeny=any
...
# Allow binding ports within 10000-65535 range over IPv4/UDP.
[Service]
SocketBindAllow=ipv4:udp:10000-65535
SocketBindDeny=any
...
```

DeviceAllow=

Control access to specific device nodes by the executed processes. Takes two space-separated strings: a device node specifier followed by a combination of r, w, m to control reading, writing, or creation of the specific device node(s) by the unit (mknod), respectively. On cgroup-v1 this controls the "devices.allow" control group attribute. For details about this control group attribute, see Device Whitelist Controller[9]. In the unified cgroup hierarchy this functionality is implemented using eBPF filtering. The device node specifier is either a path to a device node in the file system, starting with /dev/, or a string starting with either "char-" or "block-" followed by a device group name, as listed in /proc/devices. The latter is useful to allow-list all current and future devices belonging to a specific device group at once. The device group is matched according to filename globbing rules, you may hence use the "*" and "?" wildcards. (Note that such globbing wildcards are not available for device node path specifications!) In order to match device nodes by numeric major/minor, use device node paths in the /dev/char/ and /dev/block/ directories. However, matching devices by major/minor is generally not recommended as assignments are neither stable nor portable between systems or different kernel versions.

Examples: /dev/sda5 is a path to a device node, referring to an ATA or SCSI block device. "char-pts" and "char-alsa" are specifiers for all pseudo TTYs and all ALSA sound devices, respectively. "char-cpu/*" is a specifier matching all CPU related device groups.

Note that allow lists defined this way should only reference device groups which are resolvable at the time the unit is started. Any device groups not resolvable then are not added to the device allow list. In order to work around this limitation, consider extending service units with a pair of After=modprobe@xyz.service and Wants=modprobe@xyz.service lines that load the necessary kernel module implementing the device group if missing. Example:

```
...
[Unit]
Wants=modprobe@loop.service
After=modprobe@loop.service
[Service]
DeviceAllow=block-loop
DeviceAllow=/dev/loop-control
...
```

DevicePolicy=auto|closed|strict

Control the policy for allowing device access: strict

means to only allow types of access that are explicitly specified.

closed

in addition, allows access to standard pseudo devices including /dev/null, /dev/zero, /dev/full, /dev/random, and /dev/urandom.

auto

in addition, allows access to all devices if no explicit DeviceAllow= is present. This is the default.

Slice=

The name of the slice unit to place the unit in. Defaults to system.slice for all non-instantiated units of all unit types (except for slice units themselves see below). Instance units are by default placed in a subslice of system.slice that is named after the template name. This option may be used to arrange systemd units in a hierarchy of slices each of which might have resource settings applied.

For units of type slice, the only accepted value for this setting is the parent slice. Since the name of a slice unit implies the parent slice, it is hence redundant to ever set this parameter directly for slice units.

Special care should be taken when relying on the default slice assignment in templated service units that have DefaultDependencies=no set, see systemd.service(5), section "Default Dependencies" for details.

Delegate=

Turns on delegation of further resource control partitioning to processes of the unit. Units where this is enabled may create and manage their own private subhierarchy of control groups below the control group of the unit itself. For unprivileged services (i.e. those using the User= setting) the unit's control group will be made accessible to the relevant user. When enabled the service manager will refrain from manipulating control groups or moving processes below the unit's control group, so that a clear concept of ownership is established: the control group tree above the unit's control group (i.e. towards the root control group) is owned and managed by the service manager of the host, while the control group tree below the unit's control group is owned and managed by the unit itself. Takes either a boolean argument or a list of control group controller names. If true, delegation is turned on, and all supported controllers are enabled for the unit, making them available to the unit's processes for management. If false, delegation is turned off entirely (and no additional controllers are enabled). If set to a list of controllers, delegation is turned on, and the specified controllers are enabled for the unit. Note that additional controllers than the ones specified might be made available as well, depending on configuration of the containing slice unit or other units contained in it. Note that assigning the empty string will enable delegation, but reset the list of controllers, all assignments prior to this will have no effect. Defaults to false. Note that controller delegation to less privileged code is only safe on the unified control group hierarchy. Accordingly, access to the specified controllers will not be granted to unprivileged services on the legacy hierarchy, even when requested.

The following controller names may be specified: cpu, cpuacct, cpuset, io, blkio, memory, devices, pids, bpf-firewall, and bpf-devices.

Not all of these controllers are available on all kernels however, and some are specific to the unified hierarchy while others are specific to the legacy hierarchy. Also note that the kernel might support further controllers, which aren't covered here yet as delegation is either not supported at all for them or not defined cleanly.

For further details on the delegation model consult Control Group APIs and Delegation[10].

DisableControllers=

Disables controllers from being enabled for a unit's children. If a controller listed is already in use in its subtree, the controller will be removed from the subtree. This can be used to avoid child units being able to implicitly or explicitly enable a controller. Defaults to not disabling any controllers. It may not be possible to successfully disable a controller if the unit or any child of the unit in question delegates controllers to its children, as any delegated subtree of the cgroup hierarchy is unmanaged by systemd.

Multiple controllers may be specified, separated by spaces. You may also pass DisableControllers= multiple times, in which case each new instance adds another controller to disable. Passing DisableControllers= by itself with no controller name present resets the disabled controller list.

The following controller names may be specified: cpu, cpuacct, cpuset, io, blkio, memory, devices, pids, bpf-firewall, and bpf-devices.

ManagedOOMSwap=auto|kill, ManagedOOMMemoryPressure=auto|kill

Specifies how systemd-oomd.service(8) will act on this unit's cgroups. Defaults to auto. When set to kill, systemd-oomd will actively monitor this unit's cgroup metrics to decide whether it needs to act. If the cgroup passes the limits set by oomd.conf(5) or its overrides, systemd-oomd will send a SIGKILL to all of the processes under the chosen candidate cgroup. Note that only descendant cgroups can be eligible candidates for killing; the unit that set its property to kill is not a candidate (unless one of its ancestors set their property to kill). You can find more details on candidates and kill behavior at systemd-oomd.service(8) and oomd.conf(5). Setting either of these properties to kill will also automatically acquire After= and Wants= dependencies on systemd-oomd.service unless DefaultDependencies=no.

When set to auto, systemd-oomd will not actively use this cgroup's data for monitoring and detection. However, if an ancestor cgroup has one of these properties set to kill, a unit with auto can still be an eligible candidate for systemd-oomd to act on.

ManagedOOMMemoryPressureLimit=

Overrides the default memory pressure limit set by oomd.conf(5) for this unit (cgroup). Takes a percentage value between 0% and 100%, inclusive. This property is ignored unless ManagedOOMMemoryPressure=kill. Defaults to 0%, which means to use the default set by oomd.conf(5).

ManagedOOMPreference=none|avoid|omit

Allows deprioritizing or omitting this unit's cgroup as a candidate when systemd-oomd needs to act. Requires support for extended attributes (see xattr(7)) in order to use avoid or omit. Additionally, systemd-oomd will ignore these extended attributes if the unit's cgroup is not owned by the root user. If this property is set to avoid, the service manager will convey this to systemd-oomd, which will only select this cgroup if there are no other viable candidates.

If this property is set to omit, the service manager will convey this to systemd-oomd, which will ignore this cgroup as a candidate and will not perform any actions on it.

It is recommended to use avoid and omit sparingly, as it can adversely affect systemd-oomd's kill behavior. Also note that these extended attributes are not applied recursively to cgroups under this unit's cgroup.

Defaults to none which means systemd-oomd will rank this unit's cgroup as defined in systemd-oomd.service(8) and oomd.conf(5).

## DEPRECATED OPTIONS
The following options are deprecated. Use the indicated superseding options instead:

CPUShares=weight, StartupCPUShares=weight

Assign the specified CPU time share weight to the processes executed. These options take an integer value and control the "cpu.shares" control group attribute. The allowed range is 2 to 262144. Defaults to 1024. For details about this control group attribute, see CFS Scheduler[4]. The available CPU time is split up among all units within one slice relative to their CPU time share weight. While StartupCPUShares= only applies to the startup phase of the system, CPUShares= applies to normal runtime of the system, and if the former is not set also to the startup phase. Using StartupCPUShares= allows prioritizing specific services at boot-up differently than during normal runtime.

Implies "CPUAccounting=yes".

These settings are deprecated. Use CPUWeight= and StartupCPUWeight= instead.

MemoryLimit=bytes

Specify the limit on maximum memory usage of the executed processes. The limit specifies how much process and kernel memory can be used by tasks in this unit. Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size is parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. Alternatively, a percentage value may be specified, which is taken relative to the installed physical memory on the system. If assigned the special value "infinity", no memory limit is applied. This controls the "memory.limit_in_bytes" control group attribute. For details about this control group attribute, see Memory Resource Controller[11]. Implies "MemoryAccounting=yes".

This setting is deprecated. Use MemoryMax= instead.

BlockIOAccounting=

Turn on Block I/O accounting for this unit, if the legacy control group hierarchy is used on the system. Takes a boolean argument. Note that turning on block I/O accounting for one unit will also implicitly turn it on for all units contained in the same slice and all for its parent slices and the units contained therein. The system default for this setting may be controlled with DefaultBlockIOAccounting= in systemd-system.conf(5). This setting is deprecated. Use IOAccounting= instead.

BlockIOWeight=weight, StartupBlockIOWeight=weight

Set the default overall block I/O weight for the executed processes, if the legacy control group hierarchy is used on the system. Takes a single weight value (between 10 and 1000) to set the default block I/O weight. This controls the "blkio.weight" control group attribute, which defaults to 500. For details about this control group attribute, see Block IO Controller[12]. The available I/O bandwidth is split up among all units within one slice relative to their block I/O weight. While StartupBlockIOWeight= only applies to the startup phase of the system, BlockIOWeight= applies to the later runtime of the system, and if the former is not set also to the startup phase. This allows prioritizing specific services at boot-up differently than during runtime.

Implies "BlockIOAccounting=yes".

These settings are deprecated. Use IOWeight= and StartupIOWeight= instead.

BlockIODeviceWeight=device weight

Set the per-device overall block I/O weight for the executed processes, if the legacy control group hierarchy is used on the system. Takes a space-separated pair of a file path and a weight value to specify the device specific weight value, between 10 and 1000. (Example: "/dev/sda 500"). The file path may be specified as path to a block device node or as any other file, in which case the backing block device of the file system of the file is determined. This controls the "blkio.weight_device" control group attribute, which defaults to 1000. Use this option multiple times to set weights for multiple devices. For details about this control group attribute, see Block IO Controller[12]. Implies "BlockIOAccounting=yes".

This setting is deprecated. Use IODeviceWeight= instead.

BlockIOReadBandwidth=device bytes, BlockIOWriteBandwidth=device bytes

Set the per-device overall block I/O bandwidth limit for the executed processes, if the legacy control group hierarchy is used on the system. Takes a space-separated pair of a file path and a bandwidth value (in bytes per second) to specify the device specific bandwidth. The file path may be a path to a block device node, or as any other file in which case the backing block device of the file system of the file is used. If the bandwidth is suffixed with K, M, G, or T, the specified bandwidth is parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes, respectively, to the base of 1000. (Example: "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 5M"). This controls the "blkio.throttle.read_bps_device" and "blkio.throttle.write_bps_device" control group attributes. Use this option multiple times to set bandwidth limits for multiple devices. For details about these control group attributes, see Block IO Controller[12]. Implies "BlockIOAccounting=yes".

These settings are deprecated. Use IOReadBandwidthMax= and IOWriteBandwidthMax= instead.

## SEE ALSO
systemd(1), systemd-system.conf(5), systemd.unit(5), systemd.service(5), systemd.slice(5), systemd.scope(5), systemd.socket(5), systemd.mount(5), systemd.swap(5), systemd.exec(5), systemd.directives(7), systemd.special(7), systemd-oomd.service(8), The documentation for control groups and specific controllers in the Linux kernel: Control Groups v2[2].

## NOTES
1.

New Control Group Interfaces

https://www.freedesktop.org/wiki/Software/systemd/ControlGroupInterface/

2.

Control Groups v2

https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html

3.

Control Groups version 1

https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/

4.

CFS Scheduler

https://www.kernel.org/doc/html/latest/scheduler/sched-design-CFS.html

5.

sched-bwc.txt

https://www.kernel.org/doc/Documentation/scheduler/sched-bwc.txt

6.

Memory Interface Files

https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#memory-interface-files

7.

Process Number Controller

https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/pids.html

8.

IO Interface Files

https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#io-interface-files

9.

Device Whitelist Controller

https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/devices.html

10.

Control Group APIs and Delegation

https://systemd.io/CGROUP_DELEGATION

11.

Memory Resource Controller

https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/memory.html

12.

Block IO Controller

https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/blkio-controller.html


systemd.scope

title: systemd.scope(5)

summary: Scope unit configuration

text:
# systemd.scope(5)

## NAME
systemd.scope - Scope unit configuration

## SYNOPSIS
scope.scope

## DESCRIPTION
Scope units are not configured via unit configuration files, but are only created programmatically using the bus interfaces of systemd. They are named similar to filenames. A unit whose name ends in ".scope" refers to a scope unit. Scopes units manage a set of system processes. Unlike service units, scope units manage externally created processes, and do not fork off processes on its own.

The main purpose of scope units is grouping worker processes of a system service for organization and for managing resources.

systemd-run --scope may be used to easily launch a command in a new scope unit from the command line.

See the New Control Group Interfaces[1] for an introduction on how to make use of scope units from programs.

Note that, unlike service units, scope units have no "main" process: all processes in the scope are equivalent. The lifecycle of the scope unit is thus not bound to the lifetime of one specific process, but to the existence of at least one process in the scope. This also means that the exit statuses of these processes are not relevant for the scope unit failure state. Scope units may still enter a failure state, for example due to resource exhaustion or stop timeouts being reached, but not due to programs inside of them terminating uncleanly. Since processes managed as scope units generally remain children of the original process that forked them off, it is also the job of that process to collect their exit statuses and act on them as needed.

## AUTOMATIC DEPENDENCIES

### Implicit Dependencies
Implicit dependencies may be added as result of resource control parameters as documented in systemd.resource-control(5).

### Default Dependencies
The following dependencies are added unless DefaultDependencies=no is set:

•Scope units will automatically have dependencies of type Conflicts= and Before= on shutdown.target. These ensure that scope units are removed prior to system shutdown. Only scope units involved with early boot or late system shutdown should disable DefaultDependencies= option.

## OPTIONS
Scope files may include a [Scope] section, which carries information about the scope and the units it contains. A number of options that may be used in this section are shared with other unit types. These options are documented in systemd.kill(5) and systemd.resource-control(5). The options specific to the [Scope] section of scope units are the following:

RuntimeMaxSec=

Configures a maximum time for the scope to run. If this is used and the scope has been active for longer than the specified time it is terminated and put into a failure state. Pass "infinity" (the default) to configure no runtime limit.

## SEE ALSO
systemd(1), systemd-run(1), systemd.unit(5), systemd.resource-control(5), systemd.service(5), systemd.directives(7).

## NOTES
1.

New Control Group Interfaces

https://www.freedesktop.org/wiki/Software/systemd/ControlGroupInterface/